Today's wireless communication systems provide a broad range of services to both individual subscriber units and groups of subscriber units while they move about. These services include cellular telephony, group dispatch, and packet data, to name just a few. A typical example of such a system 100 is illustrated in FIG. 1. The configuration shown in FIG. 1 is typical in wireless communications systems such as Global System for Mobile Communications (GSM), Advanced Mobile Phone Service (AMPS), Terrestrial Trunked Radio (TETRA), "IDEN", and "SMARTZONE" systems. As shown, a central switch 101 provides connections between cell sites 104-107. A plurality of subscriber units 110-115 wirelessly communicate with the sites 104-107 and each other, and are often logically divided into various subgroups or talk groups. In such a system, the call processing management and switching functionality are generally contained within the same physical unit, i.e., the central switch 101. The sites 104-107 are connected to the central switch 101 through dedicated or on-demand links and intermediate processors 102-103 in what is often called a "star" configuration. Some very large systems use a hierarchy of such "stars" where intervening concentrators group the links from multiple cell sites and do some lower level processing on them before passing them up to the central switch.
Wireless communication networks as described above typically use a centralized mobility management function. As subscriber units move from one site to another they indicate their movement to the network through handover and location update procedures. The location change information is forwarded to a hierarchical network of location databases, usually called visitor location registers (VLRs) and home location registers (HLRs). The centralized connection management functionality in the switching hub uses this location information to determine which cell sites need to be included when a call request is made. While such configurations and operation generally meet current communication needs, centralized or hierarchical topology suffers from a number of problems.
First, the physical link backhaul required to carry all cell links to a central switching hub can be quite cost prohibitive, especially in cases where the lines are leased. In a typical system, all communications traffic is routed back to the central switch hub. This is particularly problematic when the switch is located far from the cell sites. Furthermore, the extensive resulting network typically needs to be configured at the start of each call. That is, each time a call request is made, network connections must be established before the call can proceed. This adds to otherwise undesirable processing delays.
Current systems also suffer from the risk of a single point of failure. That is, if the central switch itself goes down or is cut off from the network, large amounts of call traffic will be lost, and new call requests cannot be honored. The ability to connect call traffic from cell site to cell site, or cell site to telephone network is greatly impacted. Likewise, in hierarchical mobility databases, the mobility information for all subscribers that are currently located in a given system (which may contain hundreds of cell sites) is typically contained within the VLR associated with the central switch. If the VLR is somehow cut off from the network or fails, or if the HLR cannot be reached, calls to and from subscriber units are impacted and in many cases cannot be connected.
Furthermore, many switch vendors provide expensive equipment in which call processing software and connection processing software are bundled in the switching node itself. Mobility (location) and provisioning (authorization) information are also traditionally tightly bound together. As such, current HLR and VLR databases contain a combination of a subscriber's dynamic location information as well as its relatively more static provisioning parameters. This bundling of functions leads to expensive system solutions that are difficult to scale down.
Therefore, a need exists for a non-hierarchical wireless communication system that decentralizes mobility processing. Such a system should provide easy scalability and should minimize or eliminate network connection processing at call initiation.